The various T antigens of SV40 will be subjected to simple, comparative primary structure analysis in an effort to ascertain which early region sequences encode the middle (55K plus 57K) and micro (8K) T proteins. Studies designed to assess whether these proteins contain host sequences are also in progress. The large T antigen will be microinjected into various cell types with a view towards assessing whether an abortive state of neoplastic transformation will ensue. In addition, comparative DNA binding studies between the large T antigens from transformed and lytically infected cells will be undertaken.